Insulators are used with electrical transmission and distribution systems to isolate and support electrical conductors above the ground for overhead power distribution and transmission. Tie-wire and clamping mechanisms are used to secure and hold electrical conductors that are strung between utility poles in a variety of common configurations, such as roadside (tangent) or road crossing (angled) spans between the utility poles. For tangent and small angle configurations, typically up to 5°, the electrical conductors are supported on the top portion of the insulator, known as the top saddle. On angled configurations, typically greater than 5°, the electrical conductors are supported on the side portion of the insulator, known as the neck or side saddle. For the most part these needs have been met by use of a tie-wire, a pre-formed tie-wire, a clamp-top fitting, or an integral vise-top.
Tie-wire is a low-cost material, but may not achieve the desired conductor grip strength due to variation in hand-tying methods by installation personnel. It may also lack consistency in grip strength from one location to the next although the same tying method is utilized. Another deficiency of tie-wire is the required method of wrapping the wire about the neck of the insulator effectively reduces the electrical resistance path to ground. Preformed tie-wire overcomes the tie-wire deficiency in strength and consistency, but shares the issue of reducing the resistance path to ground. Preformed tie-wires carry a higher per unit cost and also require several different models to accommodate the wide range of conductor sizes and configurations used in the field.
Clamp-top fittings typically consist of a metal bracket for attachment to the insulator neck and an additional metallic assembly to keep and clamp the conductor. Clamp-top fittings generally accept a wide range of conductor sizes, but still require multiple models to cover the full range of conductor sizes and insulator neck sizes. There is a high per unit cost and a high installation cost when compared to ties. Their top saddle position also raises the conductor some distance (e.g. 3-inch) above the normal conductor mounting position which can increase the moment (force) applied to mounting hardware in small angle configurations. This has the drawback of forcing the user to shift the installation to a side-saddle position, with an associated reduction in resistance path to ground and dry-arc distance, for small angles that would otherwise be accommodated in the top saddle position by tie-wire methods.
Vise-top insulators are generally formed on insulator bodies having opposing jaws positioned at the top of the insulator body. The opposing jaws include at least one jaw piece that is adjustable relative to the other jaw piece, such that the jaw pieces can be clamped on an electrical conductor therebetween and retain it in place. Vise-top insulators overcome many of the deficiencies cited for devices above by accommodating a wide range of conductor sizes in a single model. However, the conductor grip strength is generally less than that of preformed ties and clamp-top fittings.
There has long been a need to reliably and economically secure a wide range of electrical conductor sizes to the insulator. Conventional insulators and associated ties or clamps, as cited above, generally accommodate the reliability aspects of tangent configurations. However, for angled configurations typically greater than 5° the electrical conductors are supported on the side saddle and these conventional insulators often are unable to provide the necessary mechanical and electrical support to ensure safe and proper functioning of the electrical conductor over the expected lifetime. They are also unable to provide the flexibility within one device to accommodate the wide range of conductor sizes, types, configurations and grip strength requirements.
Thus, a heretofore unaddressed need exists in the industry to address the aforementioned deficiencies and inadequacies.